a fold in pleat in the middle of the shoulder yoke

shoulder yoke 肩膀横担
估计是我们说的 垫肩...

这句话意思就是在肩膀横担上的皱褶

shoulder yoke:a fitted part of an item of clothing, a strip which goes around the shoulders, to which is sewn a looser piece of material
上衣抵肩，裙腰。
P.S.如果想要知道具体是什么样子的话，可以去百度图片上搜搜看～～